Sounds like the wrong Meds. If the infection is Viral instead of Bacterial or Vice Versa the meds only suppress it for the time it's taking them... Then returns after meds are stopped. As far as the change in location of the swelling its no different than any infection spreading I would think.
As far as relocating him that doesnt make sense. A PVC enclosure is 100x's better for heating/humidity than a Glass Tank. I dont know what your current set up is but if it is hard maintaining temps something else is a factor. Possibly the size if the heating element itself, bad thermostat or your Home is to cold. Once your room or house itself drops below 68 you have to step up the heating game. In a cool house the best is a UTH for Hot Hide and then either a RHP, CHE or Lamp for cool hide...
If all else fails and your home is to cool and you cant raise its temps (for whatever reason) put another UTH under the Cool side hide set to 80. That way each hide is sufficient for your snake.